ADENOVIRUSES are human pathogens that commonly infect the respiratory and gastrointestinal tracts.1 Adenovirus infections are endemic, particularly among children, but also may cause epidemics of pharyngoconjunctival fever, keratoconjunctivitis, gastroenteritis, and acute respiratory disease (ARD) among military trainees. Outbreaks of ARD among adults in the civilian sector are rare.2 In March 1997, an outbreak of acute respiratory disease (ARD) caused by adenovirus serotype 11 occurred among students at a job training facility in South Dakota. This report summarizes the epidemiologic and clinical features of this outbreak and discusses the change in availability of adenovirus vaccines for military use. The facility provides high school education and vocational training for 240 persons aged 16-21 years. New students matriculate year-round at 2-week intervals and remain for approximately 1-2 years. All students live on campus in one of four barracks-style dormitories (three for males and one for females). Sixty students are housed in each dormitory, with six to 10 persons per room sleeping in bunk beds. Students share a common dining hall. Routine medical care is provided by an infirmary nurse, who refers more severe illnesses to visiting physicians or local hospitals. Hospitalization discharge summaries are forwarded to the infirmary nurse.

Following the outbreak, a chart review was conducted at the facility's infirmary by the infirmary nurse. A case of lower respiratory tract infection (LRTI) was defined as physician-diagnosed pneumonia, an abnormal chest radiograph, or rales or wheezing on pulmonary auscultation in any student. A case of upper respiratory tract infection (URTI) was defined as coryza and sore throat without LRTI in any student. A case of ARD was defined as either URTI or LRTI in any student.

During March 8-28, a total of 146 (61%) students were diagnosed with ARD; 103 (71%) had URTI and 43 (29%) had LRTI. The ARD attack rate was higher among males than females (69% versus 37%, respectively, p <0.01). Although students with URTI and LRTI were similar in age and sex, frequencies of associated signs and symptoms differed between the two groups. Students with URTI were more likely than students with LRTI to have headache. Students with LRTI were more likely to have fever ≥101 F (≥38.3 C), pleuritic chest pain, shortness of breath, lymphadenopathy, vomiting, conjunctivitis, and dysuria (all p-values <0.05). Students with LRTI had higher fevers than students with URTI (median maximum temperatures: 103 F [39.4 C] versus 102 F [38.9 C], p <0.001). Five (12%) of 43 students with LRTI were hospitalized for 3 to 7 days each. One ill student with a poorly controlled seizure disorder suffered a respiratory arrest and required intensive care. Staff members at this facility also reported ARD symptoms during this time period.

Throat swab specimens were collected from seven ill students and inoculated into RMK and A549 cells. Six specimens yielded adenovirus, identified as subgenus B by the polymerase chain reaction assay, and as adenovirus 11 by microneutralization assays.3,4 The sequences of a one kilobase region of the fiber gene were identical for all isolates, suggesting a single outbreak strain.

Although adenovirus-associated ARD outbreaks among military training populations are well-described, they have not been recognized among college students or other young adults in the civilian sector. However, the setting of this outbreak of adenovirus ARD is similar to settings of previous military ARD outbreaks. In both settings, young adults live in crowded conditions, and new groups of potentially susceptible persons are introduced regularly. This outbreak differed from military outbreaks because most adenovirus-associated ARD outbreaks among U.S. military trainees are associated with adenoviruses 4 and 7. Adenovirus 11 is most commonly recognized as a cause of hemorrhagic cystitis, acute hemorrhagic conjunctivitis, and illnesses among immunocompromised persons1,5 and has rarely been associated with ARD in military trainees or in any other immunocompetent adult population.6

Outbreaks of adenovirus-associated ARD were common among U.S. military trainees before the 1970s, when routine vaccination of this group with oral vaccines against adenovirus serotypes 4 and 7 was instituted.7,8 Although these vaccines were highly effective, their manufacture has been discontinued.9 Residual supplies of the vaccines will probably be exhausted in 1999, at which time large ARD outbreaks in military settings are expected, primarily in winter months.9 This outbreak underscores that adenoviruses can cause outbreaks of ARD among young adults, persons living in crowded conditions, and military recruits.